One "trick" that manufacturers use to expand their product lines is to sell identical cards under multiple model numbers. To create differences among the various types, they lock out certain features such as a portion of the pipelines. In some cases, these locked features can be unlocked, permitting you to improve your card.

To be fair to them, they sometimes lock things due to failed tests. For example, a 16 pipeline card may have 2 pipelines fail. They may lock 4 pipes instead of 2 just because the next card in their product line has 12 pipelines. In that scenario, you may be able to open the two "good" ones, leaving you with something better than you had but not as good as the base model.

Is that clear as mud?

Someone more familar with me will have to comment on your specific card.

What is unlocking a video card? I've read it a few times, having to do with pipelines or something. Can someone explain this to me ? And does a Radeon 9800 Pro need unlocking?

If you do a mod like this then basically you'll "unlock" features of higher models and get a nice performance increase.
There's a possibility that you can mod your card into an XT. First you need to establish if you have an R350 or R360 core by counting the memory chips. If you have 8 you can flash to XT, but if you have 16 you can't I'm afraid.
If you need a guide let me know.

Okay, first verify that your card can run at XT speeds which is 412Mhz on the core and 365Mhz on the memory by using ATI Tool. Leave for about an hour without any artifacts.
If you get a clean run then you can just flash an XT bios and then overclock some more, if you do get artifacts then I can do a modified bios for you with your max clock speeds.
Let me know how you go on and i'll sort you out the bios and flashing instructions.